Bleaching compositions and methods



3,532,634 BLEACEHNG COMPOSITIONS AND METHODS William G. Woods, Fullerton, Califi, assignor to United States Borax & Chemical Corporation, Los Angeles, Calif., a corporation of Nevada No Drawing. Continuation-impart of application Ser. No. 530,789, Mar. 1, 1966. This application Apr. 14, 1969, Ser. No. 816,102

Int. Cl. Clld 7/54; D061 3/00 U.S. Cl. 25295 27 Claims ABSTRACT OF THE DISCLOSURE Activated persalt bleaching compositions containing an inorganic persalt, a water-soluble salt of a transition metal having an atomic number of 24 to 29, inclusive, an oxidatively stable chelating agent and a persalt activator agent. The bleaching compositions can be formulated with the usual detergent materials to provide a detergent-persalt bleach combination.

This application is a continuation-in-part of my copending application Ser. No. 530,789 filed Mar. 1, 1966, now abandoned.

This invention relates to bleaching compositions and Therefore, there has been proposed in the art the use of activators or accelerating agents which increase the bleaching action of the persalt at lower temperatures. Typical among these activating agents are the organic anhydrides such as succinic anhydride and phthalic anhydride, substituted phenyl esters of aliphatic acids such as sodium p-acetoxybenzenesulfonate and -N,'N-diacyl compounds. Although these activating agents are effective, they still do not activate the persalt sufliciently to obtain bleaching action comparable to that obtained by use of the chlorine-type bleaches at relatively low washing temperatures.

This invention provides novel bleaching compositions based on inorganic persalts which have excellent bleaching action at low washing temperatures, which is surprisingly comparable to the bleaching action obtained with the chlorine-type bleaches. Such activity has heretofore been impossible with the persalt type bleaching agents.

The bleaching compositions of this invention comprise a solid inorganic persalt bleaching agent, a water-soluble salt of a transition metal having an atomic number of from 24 to 29, inclusive, an oxidatively stable chelating agent, and a persalt activator agent. It has surprisingly been found that the present bleaching compositions are far superior to persalt bleaching agents activated by the heretofore known activating agents. The combinations of this invention provide a synergistic bleaching activity which is far better than that obtained by persalts activated with the single compounds.

The various ingredients of the bleaching composition are present in the bleaching solution in the following approximate molar proportions:

Patented Oct. 6, 1970 Persalt about 1 Transition metal do 0.00050.01 Chelating agent do 0.0010.1 Persalt activator do 0.05-15 Preferably the molar proportion is about 0.001-0.005 of transition metal to about 0.01-0.05 of the chelating agent to about 0.3-1.0 persalt activator to about 1 of the persalt.

The persalts applicable in the present composition are the solid inorganic persalt bleaching agents such as the alkali metal perborates, persulfates, percarbonates, perpyrophosphates and persilicates, the sodium and potassium salts being especially useful. Sodium perborate is the presently preferred persalt.

The transition metals applicable to the present invention are derived from the water-soluble salts of the transition metals having an atomic number of from 24 to 29, inclusive. Inorganic and organic salts such as the chlorides, sulfates, nitrates, perchlorates, acetates and watersoluble oxides of chromium, manganese, iron, cobalt, nickel, copper, and the like, are typical of the salts which are useful. Cobalt, manganese, and copper salts are especially useful and are presently preferred. The metal salts can be combined with certain of the chelating agents to form salts or neutral compounds which serve to provide both the metal and the chelating agent in the composi tions. Such combinations are also included within the scope of the invention.

The chelating agents applicable to the present invention are those which are oxidatively stable, that is, those which are not readily oxidized in the bleaching solution. These chelating agents preferably have a first complex formation constant with the transition metal ion of log 2 to about log 10 at about 20 C. See Stability Constants of Metal-Ion Complexes, Chemical Society (London), Special Publication No. 17, 1964. Typical chelating agents which can be used are pyrrolidine-Z-carboxylic acid, pyridine-2,6-dicarboxylic acid, picolinic acid, dipicolinic acid, 6-methylpicolinic acid, isonicotinic acid, quinolinic acid, isocinchomeronic acid, 1,10-phenanthroline and the alkyl substituted derivatives thereof, 2,2'-bipyridine, and the like. These chelating agents form complexes with the transition metals which are oxidatively stable. Well known chelating agents such as ethylenediaminetetraacetic acid and 1,2 diaminocyclohexane-N,N,N,N'-tetraacetic acid, have complex formation constants with the instant metal ions of above log 10, and are unsuitable in the present bleaching compositions.

The persalt activators are the well-known accelerators or activating agents for persalt bleaching agents, such as the organic acid anhydrides, phenyl esters of aliphatic acids having electronegative substituents on the phenyl ring, N,N-diacyl compounds, and acylcyanurates. Typical activating agents suitable for the present compositions are the following:

Anhydrides:

succinic anhydride phthalic anhydride adipic anhydride maleic anhydride chlorobenzoic anhydride benzoic anhydride glutaric anhydride acetic anhydride isophthalic anhydride Such anhydrides can be defined as preferably being derived from:

(a) aliphatic monocarboxylic acids of one to about six carbon atoms,

3 (b) aliphatic dicarboxylic acids of 3 to about 12 carbon atoms, or (c) mono and dicarboxylic acids of benzene.

Esters:

sodium p-acetoxybenzenesulfonate acetylsalicyclic acid chloroacetylsalicyclic acid sodium p-butyroxybenzenesulfonate p-acetoxybenzoic acid chloroacetylphenol-4 potassium sulfonate 3,4,5-tri(chloroacetyl) gallic acid These esters can be defined preferably as phenyl esters of aliphatic acids of up to about carbon atoms having electronegative su-bstituents on the phenyl ring, said substituents being selected from the carboxyl groups and sulfonic acid groups. The carboxyl and sulfonic acid groups can be in the form of either the free acids or salts. Also, the aliphatic acid moiety can be halogenated such as in the case of chloroacetyl. See British Pat. 864,798 and U.S. Pat. 3,130,165 for other typical examples.

N,N-diacyl compounds: N,N-diacetylaniline tetraacetylmethylenediamine triacetylmethylenediamine tetraacetylhydrazine N,N-diacyl compounds: tripropionylhydrazine N,N-diacetyl-N-benzoylhydrazine tetraacetylhexamethylenediamine N,N-diacetyl-p-toluidine N,N-diacetyl-p-chloroaniline N,N-dibutyrylaniline triacetylhydrazine tetraacetylethylenediamine Acylcyanurates:

triacetylcyanurate tripropionylcyanurate diacetylcyanurate dicyclohexanoylcyanurate The N,N-diacyl compounds and acylcyanurates can be defined as preferably N-acylated anilines, hydrazines, lower alkylenediamines (preferably with 1-6 carbon atoms in the alkylene group) and cyanurates in which the acyl moiety has up to about 6 carbon atoms. See US. Pat. Nos. 3,163,606 and 3,332,882 for typical examples of this class of compounds.

The activating agents generally have some solubility in the aqueous bleaching solution. However, since only very small amounts are employed, a very slight water solubility is all that is required.

The textile materials to be bleached are treated with the bleaching composition in aqueous solution. Preferably, the bleaching compositions are formulated with detergents and/or other laundry additives such as water softeners, antiredeposition agents, corrosion inhibitors, and the like. Therefore, also provided by this invention are laundry detergent compositions comprising one or more synthetic organic detergents or soaps and the bleaching compositions. Such detergent formulations provide a superior fabric washing composition for use at moderate washing temperatures. The bleaching action provided by the bleaching composition is equivalent to that obtained by use of chlorine-type bleaches, such as sodium hypochlorite and the chlorinated cyanuric acids.

The following examples are presented to illustrate this invention but the invention is not to be considered restricted to the specific examples given.

EXAMPLE I Washing tests using various activator compositions were conducted with Tide, a commercially available heavy duty detergent, and sodium perborate. The washing solutions contained 0.1% Tide and 0.125% sodium perborate. The tests were conducted using a Model 7243 Terg-O-Tometer apparatus, manufactured by US. Testing Company, Inc., Hoboken, N]. This apparatus consists of four 2000 ml. stainless steel beakers immersed in a constant temperature water bath maintained at F. Each beaker is fitted with a stainless steel agitator which is set to oscillate at rpm. in these tests.

The procedure involves adding 750 ml. of distilled water to the beaker and allowing the system to equilibrate at the desired temperature. Tide detergent (0.75 grams: 0.1%) then is added with agitation. After 1 minute of agitation, three swatches of cloth, 4 x 5 inches, are added. With continuous agitation, the desired reagents are added at 1 minute intervals and the agitation continued for 15 minutes after the last reagent is added. The switches then are removed from the wash solution, shaken with 400 ml. of distilled water, squeezed by hand, further rinsed in a running stream of distilled water on both sides, wrung by hand, and then ironed on the nonreflectance side.

Reflectance measurements were made before and after washing using Gardner Laboratories Multi-Purpose Reflectometer No. 1478 with a green filter. Standard tile Ser. No. R2712-59 (64.1 reading) was used with unbleached muslin samples and standard tile No. R-2717-59 (14.5 reading) was used with the EMPA cotton Bleach Test Cloth #1, Testfabrics, Inc., New York, N.Y. The percentage increase in reflectance "was calculated as follows:

Percent increase= The increases are averaged for the three swatches in each run and reported as the mean. The increase in reflectance attributed to the activator system was calculated by taking the percent increase in reflectance obtained with the persalt activator, chelated metal ion, or combinations thereof, and subtracting the percent increase obtained by sodium perborate alone (15.5). The difference is the percent increase in reflectance attributed to the activator system and was expressed as Reflectance Increase. The results are recorded in Table I in which the amounts represent the concentration of activator ingredients expressed as millimoles per liter.

TABLE I Reflectance N0. Activator system Amount increase 1 Acetic anhydride 8. 14 23. 7 2 ..do 4.07 7.6 8. 12 2. 3 12. 21 19. 0 8. 14 13. 4 1. 63 1. 5 16. 2 26. 3 12. 0 12. 6 8. 1 4. 4 0 8. 13 10. 0 11 Phthalic anhydridc 8. 14 1. 0 12 Cobaltous chloride 0.03 7 licolinic acid 0.25 i l3 Acetic anhydride... 8. 14

Cobaltous chloride 0.03 115. 7 Picolinic acid 0.25 14 Succinic anhydride. 8.12 1

Cobaltous chloride 0.03 23. 1 Picolinic acid 0.25 I 15 Sodium p-acetoxybenzcnesulfonat 8.14

Cobaltous chloride 0.03 92. 0 Picolinic acid O. 25 16 Phthalic anhydride... 8. 14 I Cobaltous chloride. 0.03 16. O Picolinic acid 0.25 l 17 Tetraacetylhydrazine. 16. 2

Cobaltons chloride. 0.03 149. 8 Picolinic acid 0. 25 18 Tetraacetylhydrazin 8. 1

Cobaltous chloride 0. 015 106. 3 Picolinic acid 0.25

10 'lriacetylcyanuratc 8. l3

Cobaltous chloride 0.03 06. 4 licollnic aci(l 0.25 20 Ferrous sulfate 0.03 1 5 2,6'dicarb0xypyridinc 0. 25 T Reflectance No. Activator system Amount increase 21111.11... Acetic anhydride 1. 4.07

Ferrous sulfate. .1 1 0. 03 12. 8 2,6-dicarboxypyridine 1 1. 0. 25 22 Sodium p-acetoxybenzenesulfonate.1... 8.14

Ferrous sulfate 0. 03 20. 9 2,6-dicarboxypyridine 1 1 0. 25 23 1. Cobaltous chloride 1... 0.03 if 1 1,10-phenanthroline- 1 1 1 0. 275 24 Acetic anhydride.. 1... 8. 14

Cobaltous chloride 0. 03 124. 9 1,10-phenanthroline 1. .1. 0. 275 25 Sodium pacetoxybenzenesulfonate. 1 8.14

Cohaltous chloride .1 0.03 157. 4 1,10-phenanthroline 1 1 1 0. 275 26 1 Tctraacetylhydrazine .1 12. 0

Cobaltous chloride 1. .1 0. 03 134. 3 1,10-phenanthroline 1 1 .1 0. 275 27 1. Sodium p-acetoxybenzenesulfonate.1... 1. 63

Cobaltous chloride 1. 0.03 101. 1,10-phenauthroline 0. 268 12. 21

0.03 157. 4 0. 268 0.08 0. 25 9 8. 14 Cupric sulfate.1 0.03 35. 5 2,2-bipy1'idine 0. 25 31 1. Sodium p-acctoxybenzenesulfon 8. 14

Cupric sulfate 1. 0. 015 25. 1 2,2-bipyridinc 11.1 0. 25 32 11 Cupric sulfate... 1. 0.03 5

Piconlinic acid 1 0. 25 33 11 Sodium p-acetoxybenzenesulfonate 8.14

Cupric sulfate .1 0. 03 25. 0 Picolinic aiicid1 1 1 1 1 34 Cupric su ate.... 1... 1

1,10-phenanthroline .1 1 0. 275 4 35 .1 Sodium pacetoxybenzenesulfonate 8. 14

Cupric sulfate .1 0. 03 39. 3 1,10-phenathroline 1 0. 275 36 1. Manganous sulfate 11 11 0.03 0 Picolinic acid .1 0. 25 37 Acetic anhydride 1. 8.14

M anganous sulfate 11 0. 03 71. 9 Picolinic acid 0. 25 38 .1 Nickel acctate.1 .1 1. 0. O3 0 6 Picolinio acid 1.1. .1 0.25 39 Acetic anhydride 1. 8. 14

Nickel acetate.-. 1... 1. 0.03 43. 5 Picolinic acid .1 1. 0. 25 40 .1 Cobaltous chloride 1. .1 0. 03 1 4 2,2-loipy1'idine 0. 25 41 .1 Sodium p-acetoxyloenzenc sulfonate.1 8. l4

Oobaltous chloride 1 0. 03 151. 3 2,2 -bipyridi11c 1 1 1 0. 25 42 1. Trisacetylcyanurate.1 8. 13

Cobaltous chloride. 0. 03 137. 1 2,2-bipyridine 0. 25 43 1. Acetic anhydride 6. 51

Cobaltous chlorid 0.024 159.0

2-bipyridine. 0. 2 44 1 Acetic anhydride 1 6. 51

Cobaltous chloride. 1 0.024 64. 4 2,2-bipyridinc 1 0. 2

1 Test N0. 44 was in the absence of Tide.

EXAMPLE II The procedure of Example I was followed except 2.02 grams of potassium monopersulfate were employed instead of sodium perborate. The following results were obtained.

TABLE II Reflectance Activator system Amount increase Number 45 .1 Acetic anhydride. 1 1.. 8. 14 2 46 Cobaltous chloride.... 0.03 7

Picolinio acid 1111111 0.25

47 111111111111111111 .1 Acetic anhydride. 1 1. 8. l4

Gobaltous chloride. 0. 03 13 Picolinic acid 1111111 11 0. 25

suitable detergent formulations containing the bleaching systems of the present invention.

Detergent compositions were formulated by known procedures to provide two typical compositions.

Component: Parts by Weight Sodium dodecylbenzenesulfonate 11 5 Sodium lauric acid isoethioniate 1 111111 111 11 2 Lauryl alcohol 11 0.5 Monoethanolamide of coconut oil fatty acid 1.11 0.5 Sodium tripolyphosphate 111111111111111111 11 40 Sodium silicate 111111111111111111111111111 11 3 Carboxymethyl cellulose 1111111111111111111 11 1 Sodium sulfate 11111111111111111111111111 11 38 Water 1111111111111111111111111111111111 11 10 Optical brightener 1111111111111111111111 11 1.01

The above will be referred to hereafter as Detergent A.

As an example of a typical nonionic detergent:

Component: Parts by weight Nonylphenyl condensed with 9 molecules of ethylene oxide 1111111111111111111111111 11 8 Sodium tripolyphosphate 111111111111111111 40 Sodium silicate 111111111111111111111111111 11 5 Carboxymethyl cellulose 1111111111111111111 11 1 Sodium sulfate 111111111111111111111111111 11 43 Water 111111111111111111111111111111111111 11 3 Optical brightener 1111111111111111111111 11 0.01

The latter formulation will be denoted as Detergent B. Several methods can be used in the formulation of the compositions of this invention. It is preferred that the packaging arrangement be such that the unchelated metal salt is separated from the persalt in order to avoid catalytic decomposition of the persalt before use. The organic activators generally are subject to hydrolysis because of their high reactivity and, consequently, these activators should be protected from environmental moisture.

Several methods of so protecting the organic activator can be used, one of which is encapsulation. Solid particles or liquid droplets can be encapsulated with coatings which dissolve or disperse under conditions of use. Suitable encapsulating materials include gelatin, ethyl cellulose, emulsifiable waxes, and the like. Such an encapsulated activator, in the form of solid particles, can be intermixed with a granulated detergent formulation and the persalt, the chelating agent, and the metal salt. The metal salt preferably should be combined wih the activator and encapsulated or it should be reacted with the chelating agent prior to combination with the detergent and persalt.

The following is a typical packaging arrangement.

Part I: Parts by weight Detergent A granules 1111111111111111111 11 Sodium perborate tetrahydrate 1111111111111 11 50 Picolinic acid 111111111111111111111111111 11 1.2

Part II:

Sodium p-acetoxybenzenesulfonate 1111111111 11 77 Cobaltous sulfate (anhydrous) 1111111111111 11 0.2

Components of Part II are intimately mixed and encapsulated by well-known methods. Parts I and II then are thoroughly intermixed to give a free-flowing solid composition, useful in home laundry applications. This composition also may be compressed into tablets.

A second method involves the use of composite tablets which contain the detergent, persalt, activator, metal ion, and chelating agent in various configurations. For example, a core is prepared consisting of a pellet of a compressed, intimate mixture of 20 grams of tetraacetylhydrazine, 0.06 gram of anhydrous cobaltous sulfate, 0.5 gram of starch, and 0.1 gram of talc. This core is surrounded by a coating of a mixture of 60 grams of Detergent A, 15 grams of sodium perborate tetrahydrate and 0.5 gram of 1,10-phenanthroline. Another tablet configuration can be used in which a compressed cylindrical body comprising 60 grams of Detergent B mixed with 0.56 gram persalt, and the chelating agent. The following is a typical example.

Packet 1: Grams Detergent B 60 Sodium perborate tetrahydrate Picolinic acid 0.4

Packet II:

Acetic anhydride 10 Manganous acetate 0.06

In practice, both packets are opened and the contents simultaneously poured into about 12 to about 18 gallons of water to be used for the washing and bleaching operation.

What is claimed is:

1. A bleaching composition consisting essentially of a solid, inorganic persalt bleaching agent, a water soluble salt of a transition metal having an atomic number of from 24 to 29, inclusive, an oxidatively stable chelating agent having a first complex formation constant with said transition metal ion of log 2 to log 10 at about C.,

and a persalt activator agent, the components of said bleaching composition being present in a molar proportion of:

Persalt About 1 Transition metal About 00005-001 Chelating agent About 0.001-0.1 Persalt activator About 0.05l.5

said persalt activator agent being selected from (a) the organic anhydrides derived from alkyl and alkenyl monocarboxylic acids of 1 to about 6 carbon atoms, alkyl and alkenyl dicarboxylic acids of 3 to about 12 carbon atoms or monoor dicarboxylic acids of benzene,

(b) phenyl esters of alkyl and haloalkyl carboxylic acids of up to about 5 carbon atoms having electronegative substituents on the phenyl ring, said substituents being selected from the carboxyl and sulfonic acid groups, or

(c) N-acyl compounds selected from N-acylated anilines, hydrazines, lower alkylenediamines, and cyanurates in which the acyl moiety has up to about 6 carbon atoms.

2. A detergent composition consisting essentially of a water-soluble anionic or nonionic synthetic organic detergent or soap and the bleaching composition of claim 1.

3. A bleaching composition according to claim 1 in which said persalt is sodium perborate.

4. In the method of bleaching textiles by treating said textiles with an aqueous solution of a normally solid inorganic persalt bleaching agent, the improvement which comprises activating said bleaching agent with a combination of a water-soluble salt of a transition metal having an atomic number of from 24 to 29, inclusive, an oxidatively stable chelating agent having a first complex formation constant with said transition metal ion of log 2 to log 10 at about 20 C., and a persalt activator agent in amounts sufficient to provide the following molar proportions:

Persalt About 1 Transition metal About 0.00050.01 Chelating agent About 0.0010.1 Persalt activator About 0.051.5

said persalt activator agent being selected from:

(a) the organic anhydrides derived from alkyl and 8 alkenyl monocarboxylic acids of 1 to about 6 carbon atoms, alkyl and alkenyl dicarboxylic acids of 3 to about 12 carbon atoms or monoor dicarboxylic acids of benzene,

(b) phenyl esters of alkyl and haloalkyl carboxylic acids of up to about 5 carbon atoms having electronegative substituents on the phenyl ring, said substituents being selected from the carboxyl and sulfonic acid groups, or

(c) N-acy1 compounds selected from N-acylated anilines, hydrazines, lower alkylenediamines, and cyanurates in which the acyl moiety has up to about 6 carbon atoms.

5. The method according to claim 4 in which said persalt is sodium perborate.

6. A bleaching composition consisting essentially of a solid, inorganic persalt bleaching agent, a water-soluble salt of a transition metal having an atomic number of from 24 to 29, inclusive, an oxidatively stable chelating agent having a first complex formation constant with said transition metal ion of log 2 to log 10 at about 20 C., and a persalt activator agent, the components of said bleaching composition being present in a molar proportion of Persalt About 1 Transition metal About 0.0005-001 Chelating agent About 0.001-0.1 Persalt activator About 0.05-1.5

said persalt activator agent being selected from the group consisting of succinic anhydride, phthalic anhydride, adipic anhydride, benzoic anhydride, glutaric anhydride, acetic anhydride, sodium p-acetoxybenzene-sulfonate, acetylsalicylic acid, cholroacetylsalicylic acid, sodium pbutyroxybenzenesulfonate, p-acetoxybenzoic acid, N,N- diacetylaniline, tetraacetylmethylenediamine, triacetylmethylenediamine, tetraacetylhydrazine, triacetylcyanurate, tripropionylcyanurate and diacetylcyanurate.

7. A bleaching composition according to claim 6 wherein the components are present in the following molar proportions:

Persalt About 1 Transition metal About 0.0010.005 Chelating agent About 0.010.05 Persalt activator About 0.3-1.0

8. A bleaching composition according to claim wherein said persalt is sodium perborate.

9. A bleaching composition according to claim wherein said transition metal is cobalt.

10. A bleaching composition according to wherein said transition metal is manganese.

11. A bleaching composition according to wherein said transition metal is copper.

12. A bleaching composition according to wherein said persalt activator is acetic anhydride.

13. A bleaching composition according to claim wherein said persalt activator is sodium p-acetoxybenzenesulfonate.

14. A bleaching composition according to claim 6 wherein said chelating agent is picolinic acid.

15. A bleaching composition according to claim 6 wherein said chelating agent is 1,10-phenanthroline.

16. A bleaching composition according to claim 6 wherein said persalt is potassium monopersulfate.

17. A bleaching composition according to claim 6 wherein said persalt activator is triacetylcyanurate.

18. In the method of bleaching textiles by treating said textiles with an aqueous solution of a normally solid inorganic persalt bleaching agent, the improvement which comprises activating said bleaching agent with a combination of a water-soluble salt of a transition metal having an atomic number of from 24 to 29, inclusive, an oxidatively stable chelating agent having a first complex formation constant with said transition metal ion of log 2 to log 10 claim claim claim QGQQQQ at about 20 C., and a persalt activator agent in amounts suflicient to provide the following molar proportions:

Persalt About 1 Transition metal About 00005-001 Chelating agent About 0.0010.1 Persalt activator About 0.05-1.5

said persalt activator agent being selected from the group consisting of succinic anhydride, phthalic anhydride, adipic anhydride, benzoic anhydride, glutaric anhydride, acetic anhydride, sodium p-acetoxybenzenesulfonate, acetylsalicylic acid, chloroacetylsalicylic acid, sodium p-butyroxybenzenesulfonate, p-acetoxybenzoic acid, N,N- diacetylaniline, tetraacetylrnethylenediamine, triacetylmethylenediamine, tetraacetylhydrazine, triacetylcyanurate, tripropionylcyanurate and diacetylcyanurate.

19. The method according to claim 18 in which said persalt is sodium perborate.

20. The method according to claim 18 wherein the components are present in the following molar proportions Persalt About 1 Transition metal About 0.001-0.005 Chelating agent About 0.01-0.05 Persalt activator About 0.3-1.0

21. The method according to claim 18 in which persalt is potassium monopersulfate.

22. In an aqueous persalt bleaching solution of a normally solid, inorganic persalt bleaching agent activated by about 0.05-1.5 mole of persalt activator per mole of said persalt bleaching agent, the improvement which comprises a synergistic amount of about 0.0005-0.01 mole of a water soluble-salt of a transition metal having an atomic number of from 24 to 29, inclusive, and about 0.001-0.1 mole of an oxidatively stable chelating agent having a first complex formation constant with said transition metal ion of log 2 to log 10 at about 20 0, dissolved in said aqueous solution, said molar amounts being based on one mole of said persalt bleaching agent and said persalt activator being selected from the group consisting of succinic anhydride, phthalic anhydride, adipic anhydride, benzoic anhydride, glutaric anhydride, acetic anhydride, sodium p-acetoxybenzenesulfonate, acetylsalicylic acid, chloroacetylsalicylic acid, sodium p-butyroxybenzenesulfonate, p-acetoxybenzoic acid, N,N-diacetyl aniline, tetraacetylmethylenediamine, triacetylmethylenediamine, tetraacetylhydrazine, triacetylcyanurate, tripropionylcyanurate and diacetylcyanurate.

23. A bleaching composition according to claim 22 in which said persalt bleaching agent is sodium perborate.

24. A bleaching solution according to claim 22 wherein said persalt activator is triacetylcyanurate, said transition metal is cobalt and said chelating agent is 1,10- phenanthroline.

25. A bleaching solution according to claim 22 wherein about 0.001-0.005 mole of said water-soluble salt of a transition metal and 0.01-0.05 mole of said oxidatively stable chelating agent, per mole of said persalt bleaching agent, are dissolved in said aqueous solution.

26. A bleaching solution according to claim 22 wherein said oxidatively stable chelating agent is picolinic acid.

27. A bleaching solution according to claim 25 wherein said transition metal is cobalt and said chelating agent is 1,10-phenanthroline.

References Cited UNITED STATES PATENTS 3,156,654 11/1964 Konecny et al. 3,163,606 12/1964 Viveens et al. 3,177,148 4/1965 Bright et al. 3,211,658 10/1965 Hirtz et al. 3,332,882 7/1967 Blumbergs et al. 3,338,839 8/ 1967 MacKeller et al.

MAYER WEINBLATT, Primary Examiner US. Cl. X.R. 

